There have been various tread locking devices disclosed in the prior art.
Examples of the prior art are U.S. Pat. Nos.: 4,246,947 to Ewing, dated Jan. 27, 1981; 2,152,684 to E. A. Grange, dated Apr. 4, 1939; 2,152,685 to E. A. Grange, dated Apr. 4, 1939; 1,943,881 to R. R. Ware, dated Jan. 16, 1934; 1,0577462 to F. W. Kremer, dated Apr. 1, 1913; 848,745 to J. E. Hopkinson, dated Apr. 2, 1907; 824,345 to M. A. Elliott, dated Jun. 26, 1906; 813,423 to H. Hill, dated Feb. 27, 1906; 771,947 to J. A. Swinehart, dated Oct. 11, 1904.
The previous prior art affords only marginal performance under limited conditions. The average polyurethane wheels although somewhat harder than rubber wheels, but still being resillient provide a good coefficient of friction for traction and a higher load rating when compared to rubber wheels. The present invention is far superior in that basically, it has only two parts, but yet provides the best tread locking possible along with the highest load rating possible, for a polyurethane wheel. Another feature is that a new type of wheel is created for the materials handling industry; namely, the best pallet jack load wheel to date, with a sufficient safety factor of at least 2 for the load rating, in the polyurethane class of wheels used on electric pallet jack machines. This safety factor enables the driven electric pallet jack machines to carry their rated load, not a partial load as for conventional load wheels. The present invention operates under all weather conditions. The present invention can be applied to all types of wheels, industrial, automotive, and rollers for heavy loads with low height from bottom of vehicle to floor. It is the first wheel assembly of its kind to match the weight load rating (tire load rating) of a conventional heavy truck class rating; example: conventional rubber tire used for Interstate use, conventional road use, and off the road use, etc.
The wheel assembly is also highly resistant to acids, fuels such as gasoline, diesel fuel, other liquid fuels, and other chemicals; caustic alkali materials, caustic acids, sulfuric acids, hydrochloric acids, chemical solvents, etc. This is achieved through the use of Isoplast.RTM. grade 202 material molded onto the wheel tread locking hub. This is the product for the future available today.